Magnetic convergence assembly



July 28, 1959 T. JENSEN 2,897,390

MAGNETIC coNvERGENcE ASSEMBLY 'Filed Dec. 25, 1955 17 INVENTOR.

V y zcade/eaym United States Patent O MAGNETIC CONVERGENOE lASSEMBLY Theodore Jensen, Westfield, NJ.,y assignor to Glaser- Steers Corporation, a lcorporation ofNew Jersey Application December 23, .1.955, Serial No. 554,972 s Claims. (Cl. 313-77) invention relates to a magnetic convergence device for convergingv the multiple electron beams of a cathode ray tube. It is directed particularly to the mountingmeans for supporting the magnetic and electrical components of a convergence device and to the relationship of the magneticl members to one another.

In color television the cathode ray tube receiver receives signals, each corresponding to the colors transmitted. These signals are transmitted to separate electron guns projected as separate electron beams circumferentially spaced. Along the neck of the tube a magnetic means is provided for'converging the electron beams so that the beams will strike the fluorescent screen within a given small area. Each portion ofthe screen will be energized in accordance with the combined signal of the converged electron beams Aand a spot of combined colors will be produced of the'same hue and intensity as the corresponding portions of `the vtelevised object.

Inv order to produce aclear and properv colored picture over the entire area of the fluorescent screen, a steady magnetic field is required to converge the beams over the mid-area of the `screen and an additional dynamic field is required to converge the beams in the surrounding fringe area. The'steady ux may be provided by electromagnetic coils having a` direct current pass therethrough or permanent magnets positioned around the tube to providev a field in the tube adjacent the electron beam.

An object of theinvention is to provide a mounting member for holding the magnetic and electrical components of a convergence device that is easily mounted on the neck of the cathode ray tube.

Another objectofthe invention is to provide a convergence device that isveasily assembled and inexpensive to manufacture.

A still further object of the invention is a convergence device-that accurately and uniformly controls the convergence of multiple electron beams.

Other and further objects and advantages of the invention will be lapparentffrom the following description taken in connection with thedrawings in which:

Fig. 1 is a front view of theconvergence device;

Fig. 2 is a fragmentary view of the associated mountingview of the magnetic assembly;

Fig. 3 is a side view of the magnetic assembly and associated mounting means taken along lines 3-3 of Fig. l;

Fig. 4 is a top view of the magnetic assembly and associated mounting means shown in Fig. 3;

Fig. 5 1is;a-,top-view;'of Fig: 3 without the permanent magnet;

Fig. 6 is a sectional view of the fragmentary portion along lines 6-6 Yof Fig..,5 without the electromagnetic coils; and- Fig.,L 7 is an enlargedfragmentary sectionalview of the permanent magnetand .associated mounting means.

Referring to Figs.v 1 and 2 of the drawing a mounting frame 10 is made ofa non-magnetic material preferably a plastic material. The mounting plate 10 has a tubular member 11,` split longitudinally to separate the member to form a space A between the ends 12 and 13. At respective ends are handles 14 and 15 integral with 2,897,390*4 Patented July 28, 1959 the tubular member yand extending preferably normal thereto to the handles providing means for conveniently clamping the tubular member on the neck of a cathode ray tube. Blocks 16 and 17 at the end of the handles 14 and 15 have bores 18' and 19 extending therethrough and'in alignment/to pass a threadedbolt 21. The block 16 has a recess 22 with angularly shaped walls for re'- ceiving the hexagonal head 23 of the bolt. A nut 24 is threaded on the bolt to engage block 17 and force the tubular member closed. The tubular member 11 has a cylindrical surface 26 for fitting around the outer surface ofthe tube 27.v The' handles 1'4 and 15 have ribs '28, 29'extendinglbetween the tubular member and the blocks 14 and 15 to form withV thepanels 30 and' 31 a rigidV structure for pulling the ends 12 and 13` together. Instead ofthe bolt and winged nut, a cam or spring device may be used that is turned to draw the ends together.

Theelectron beams of the cathode ray tube are circumferentiallyspaced 120 apart andpass between internal polepieces'34, 34a, 34b respectively also spaced circumferentially 120 apart; The pole pieces confine g the magnetic Held and'restrict the effect of the field to the electron beam passing therebetween. The beams are therefore independently adjustable and the convergence of the beam isdetermined by the magnetic assemblies 37,3711, 37b. The assemblies 37, 37a, 37b are positionedexternally tothe cathode ray tube and adjacent the internalpole'pieces. The assemblies create a flux that is Ysupplied to a respective internal pole piece inside of the cathoderay tube to `deflect a respective cathoderay beam; Each" assembly'comprises a permanent magnet 38 and a dynamic electromagnet 39. Since each is identical in structure the description'of assembly 37 will suflice and is applicable to each' assembly except for the addition of' the reference letters a and-b for the corresponding elements yof a respective assembly.

Thedynamic electromagnet 39 has a powdered U- shaped iron core withv twolegs l43, 44 and a cross-piece divided vvinto a'portion 45"'connected to leg 43` and a portion 46 connected'to leg 44. Coils 47, 48 on legs 43, Vi4-respectivelyI pass an alternating current in the order of 1500 kc. to create' an alternating flux in addition to the steady=fluxof the permanent magnet 38.

The powdered iron core is -spaced from the mounting plate 10 by means of the'support 51 fand the shoulders 52 `and-53 ofthe "grooves 54, 55 in the tubular member 11. The grooves 54, 55 extend longitudinally substantially half of the length of the member and are circumferentiall'yseparated by a spacer 56 which has a bottomed bore 47 'therein between the legs 43, 44. The flux density of the `magnetic; assembly may be readily measured by inserting 'an electrical instrument probe in the bore. The

' ends-ofthe legs fitin the groove and seat against the shoulders 52, 53.'Y The support 51 has posts 60, `61 and 62 spacingthe i-rorrcore from the mounting plate 10 the same distance as the `shoulders 52 and 53. The post-61 has Ia stud-63fextending between the ends of thecrossepieceportions 45, 46. V-shaped'longitudinal grooves are formed :in the ends of the cross piece portions to tit-around the stud 63 `and position the ends of the cross piece together but provide a gap B between the ends.- Af panel 65 *and sidestrips 66, 67 form grooves 68, 69 which retain the-powdered iron'core in the grooves 54, 55. The powdered iron core is rectangular in shape withsquare edges so -that the core readily ts in 'the grooves '68," 69 and'on the ilat surfaces of the posts 60, 61, .62. The grooves 52., 53 and the grooves l68, 69 are of a length to recess the iron core so that the edges offthe mounting member protect'the iron core. The Winclingsxorl coils `47, 48 are designed for a hyperbolic wave shape havinga frequency in the order of kc. Tire-.iron corefisspaced -from'f the mounting plate to a distance to accommodate the coils. The coils are formed and the legs of the iron core fitted in the windings and the magnetic assembly positioned on the mounting member by sliding the core in the grooves. Y

A U-shaped resilient non-magnetic metal strap 70 has a bowed mid-portion 71 pressing against the coils and hooked ends 72, 73 fitting into slots or-grooves 74,

75 in the mounting member 10. Thus the magnetic assembly is securely held on the mounting member. Y' I In the panel 65 a semi-circular hole is formed in which the disc-shaped permanent magnet 38 is fitted. The permanent magnet rests on the cross-piece portions 45, 46 and is held in place by a resilient clip 76 having a rectangular nger 77 and rolled portion 78. The linger 77 passes through a slot 79 positioned slightly below the exposed surface of the permanent magnet. The nger 77 is slightly curved in shape and is held under stress between the surface of the magnet and the edge of the slot. The linger 77 has knob 80 which ts into a bore or recess 81 in the magnet to Alock the magnetin place. The rolled portion provides a grip for inserting and removing the clip and extends the curved shape of the finger to hold the clip under stress.

The magnetic assemblies 37, 37a, 37b `are circumferentially spaced 120 to one another. The ends of the legs of the iron cores are positioned adjacent to the internal pole pieces to provide the shortest ilux path. The strength of the permanent or steady field may be adjusted by rotation of the permanent magnet. Increase in the field between the pole pieces deilects the beam radially inward or outward. rIhe flux from the magnet assembly varies rapidly in synchronism with the sweep of the electron beam to vary the converging iniiuence at the ends of the sweep. Y

The mounting plate and tubular member 11 along with the various posts, supports land panels may be molded as a single piece made of plastic. The posts 60, 61, 62 provide a secure base and lirm connection for the panel `65 and strips 63, 64 with the mounting plate 10. The tubular member provides a spacedsupport for the ends of the iron core as well as ladded strength for the necessary llexure of the frame to clamp the neck of the cathode ray tube. The plastic material is nonmagnetic and the grooves 54, 55 are deep.Y The portions 82, 83 that hold the magnet assembly in place are thin to provide a short flux path between the iron core and the internal pole pieces. Y

The stud 63 between the cross-piece portions 45, 46 is slightly tapered to spread the cross-piece portions against the strips `66, 67 to snugly hold the core pieces in position. The diameter of the stud 63 determines the length of the gap between the cross-piece portions. The wedging action between the stub and side strips accurately positions the core pieces so that the air gap between the magnetic poles provides optimum relative performance of the permanent liux and dynamic llux.

An advantage of the convergence device hereinbefore described is that the clamping means are the only mounting means required to hold the device on the neck of the tube. The unit can be positioned andtightened in place independently of any other support members. The device is easily assembled by hand. The legs 43, 44 are inserted in the pre-wound coils 47, 48 to form the magnet assembly. The assembly is mounted on the plate 10 by sliding the ends of the legs 43, 44 in grooves 54, 55 and the corners of the legs between the strips 66, 67 and panel 65. The square notches slide over the stud 63 to properly space the air gap. The permanent magnet is set on the cross pieces 45, 46 as the clip 76 is inserted through the slot 79 and the two members slid and locked in position. The clip 76 presses the permanent magnet against the core to maintain the permeability of the ux path constant. The permanent magnet is held from side motion by the panel 65 and from dropping from the positions bythe clips 76.

The convergence device is particularly applicable to the color television cathode ray tubes for converging the three electron beams each varying in intensity with a respective primary color to converge the beams so that each electron beam strikes the portion of the screen corresponding to the color intensities it is transmitting. y The convergence unit accurately and uniformly provides for proper convergence over the entire screen to produce a clear picture with exact color reproductions.

Various modifications and changes may be made in the embodiment described herein without departing from the invention as set forth in the 4appended claims.

I claim: I

1. A colored television convergence device comprising a U-shaped ferromagnetic core having .leg portions-and a connecting cross portion adapted to pass flux therethrough, a permanent magnet on said cross piece to provide a permanent flux through and across the openv ends of said legs, an electromagnetic coil wound on said legs, a tubular member positionable immediately adjacent to the neck of a cathode ray tube, a radially extending mounting plate secured to said tubular member and having a panel spaced from said tubular member extending lateral to said plate and generally parallel to said tubular member, said ferromagnetic core fitting snugly between said panel and said tubular member to hold said core from radial and circumferential movement and said panel and tubular member formed in a space to axially position said core and electromagnet against said plate, and means secured to said plate holding said core against said plate to prevent axial movement 'of said core and electromagnet so that said core and electromagnet are firmly xed in position. 'f

2. A colored television convergence device as claimed in claim 1 wherein a permanent magnet is provided and said panel has a recess adjacent to said connecting cross piece to rotatably hold said permanent magnet, said permanent magnet permanently positioned in said recess and leaf-spring means extending through said mounting plate resiliently pressing against said permanent magnet to hold said magnet against said cross piece and rotatably holding said magnet to provide an adjustmentrof the permanent flux passed to said core. i

3. A convergence device as claimed in-claim 1 wherein said core comprises two pieces, and a stub is mounted on said mounting plate to space adjacent'ends of said pieces to adjust the permeability of said core. f

4. A covergence device as claimedin-claim 2 Wherein said mounting panel has a slot to the rear of said permanent magnet and slightly below the plane of said permanent magnet and said spring means is a resilient strip slightly bowed through the central portion and fitting Ithrough said slot and over the top to engage said permanent magnet, and the other end of said strip being formed to hold said strip in said slot.

5. A convergence device as claimed in claim 2 wherein a pair of grooves are provided through the outer vWall of said tubular member for receiving the ends of arespective core to securely hold saidv core and ywinding in place.

References Cited in the iile of this patentl l UNITED STATES PATENTS Fisher Mar. 14,1950 

